Electrochromic system with coupled RED-OX system and special anions

ABSTRACT

The novel electrochromic system comprises at least one reducible and at least one oxidizable substance OX 2  and RED 1 , respectively, which are linked to one another via a bridge and are outstandingly suited for use in an electrochromic device.

[0001] The present invention relates to an electrochromic system, to anelectrochromic fluid comprising this electrochromic system, and to anelectrochromic device comprising this electrochromic fluid.

[0002] Electrochromic devices comprising an electrochromic system arealready known.

[0003] The electrochromic system of such devices customarily includespairs of redox substances—redox couples—dissolved in an inert solvent.Additionally, conductive salts, light stabilizers and substances whichinfluence the viscosity may be present.

[0004] The redox couple used comprises one reducible and one oxidizablesubstance each. Both are colourless or have only a weak coloration.Under the influence of an electrical voltage the one substance isreduced and the other oxidized, with at least one becoming coloured inthe process. After the voltage is switched off, the two original redoxsubstances are formed once more, which is accompanied by thedisappearance or fading of the colour.

[0005] RED₁+OX₂

OX₁+RED₂

[0006] (colourless) (coloured)

[0007] (low-energy couple) (high-energy couple)

[0008] U.S. Pat. No. 4,902,108 discloses that suitable such redoxcouples are those in which the reducible substance has at least twochemically reversible reduction waves in the cyclic voltammogram and theoxidizable substance, correspondingly, has at least two chemicallyreversible oxidation waves.

[0009] Electrochromic devices can find multivarious applications. Forexample, they may take the form of a rearview car mirror which whentravelling at night can be darkened by applying a voltage, thuspreventing the driver being dazzled by headlights of other vehicles (cf.e.g. U.S. Pat. No. 3,280,701, U.S. Pat. No. 4,902,108, EP-A-0 435 689).Such devices may also be employed in window panes or car sunroofs where,following application of a voltage, they provide shade from thesunlight. Finally, it is possible to use such devices to construct adisplay device for the graphic representation of information in the formof letters, numbers and symbols.

[0010] Electrochromic devices normally consist of a pair of glass orplastic plates, one being mirrored in the case of a car mirror. One sideof these plates is coated with a transparent, electroconductive layer,e.g. indium tin oxide (ITO). These plates are then used to construct acell: to this end their facing, electroconductively coated side isattached, preferably by means of adhesive bonding, to an annular orrectangular sealing ring. The sealing ring establishes a uniformdistance between the plates of, for example, from 0.1 to 0.5 mm. Thiscell is then filled, via an aperture, with an electrochromic solutionand then tightly sealed. By way of the ITO layer it is possible tocontact the two plates separately.

[0011] The electrochromic systems known from the prior art compriseredox couples which following the reduction and oxidation, respectively,form coloured free radicals, cationic free radicals or anionic freeradicals that are chemically reactive. As known, for example, fromTopics in Current Chemistry, Vol. 92, pp. 1-44 (1980) such (ionic) freeradicals may be sensitive to electrophiles or nucteophiles or else tofree radicals. In order, therefore, to achieve a high level of stabilityin an electrochromic device comprising an electrochromic system of thiskind—a system which is intended to withstand several thousand switchingcycles—it is necessary to ensure that the solvent used is absolutelyfree from electrophiles, e.g. protons, nucleophiles and oxygen. It mustalso be ensured that such reactive species are not formed byelectrochemical processes taking place at the electrodes duringoperation of the electrochromic device.

[0012] The back-reaction to RED₁ and OX₂ that is formulated in the aboveequation also takes place continuously away from the electrodes withinthe volume of the solution while the electrochromic device is inoperation. Owing to the above-described hazards of degradation reactionsof the (ionic) free radicals by electrophiles, nucleophiles or freeradicals it is important, for the long-term stability of the display,that the back-reaction in accordance with the above equation is able totake place as rapidly as possible and without side reactions

[0013] A frequent observation in such electrochromic devices is aseparation, known as segregation, of the coloured species OX₁ and RED₂,leading to the development in the device of coloured spots or stripesSegregation of this kind is observed, for example, when the device isnot positioned horizontally. Current flow over a prolonged period mayalso lead to such segregation. Since many of the abovementioned uses ofsuch electrochromic devices, for example in the case of car rearviewmirrors, window panes or display devices, operate with the devicepreferably in a perpendicular or near-perpendicular position and in somecases over prolonged periods of time as well, such segregation leads toserious problems.

[0014] It has now been found that by coupling RED₁ and OX₂ via acovalent chemical bond, and through the presence of specific anions inthe electrochromic solution, it is possible to suppress to a largeextent or completely eliminate such segregation.

[0015] The present invention accordingly relates to an electrochromicsystem comprising at least one oxidizable substance RED₁ which releaseselectrons at an anode, and at least one reducible substance OX₂ whichaccepts electrons at a cathode and in so doing undergo transition from aweakly coloured or colourless form into a coloured form OX₁ and RED₂,respectively, accompanied by an increase in the absorbance in thevisible region of the spectrum, the weakly coloured or colourless formbeing restored after charge equalization, characterized in that at leastone of the substances RED₁ and OX₂ that are present are linkedcovalently to one another via a bridge and in that at least one aniontype X⁻ is present which a) has a molar mass>200 g/mol, preferably>250g/mol and/or b) has a cagelike structure.

[0016] Cagelike structure means closed cages as well as such structuresderived from closed cages by removing 1 to 3 atoms of the cagelikestructure (nestlike structure).

[0017] At least one of the transitions induced by oxidation orreduction, RED₁

OX₁ or OX₂

RED₂, respectively, is associated with an increase in absorbance in thevisible region of the spectrum.

[0018] The reduction and oxidation processes in the electrochromicsystem of the invention generally take place by electrons being acceptedor released at a cathode or anode, respectively, a potential differenceof from 0.3 to 3 V preferably obtaining between the electrodes. Afterthe electrical potential has been switched off, charge equalizationtakes place—in general spontaneously—between the substances RED₂ andOX₁, accompanied by disappearance or fading of the colour. Such chargeequalization also takes place even while the current is flowing in theinterior of the electrolyte volume.

[0019] The electrochromic system of the invention preferably comprisesat least one electrochromic substance of the formula (I)

YB—Z_(a)B—Y_(b)_(c)B—Z   (I)

[0020] in which

[0021] Y and Z independently of one another represent a radical OX₂ orRED₁, subject to the proviso that at least one Y represents OX₂ and atleast one Z represents RED₁,

[0022] where

[0023] OX₂ represents the radical of a reversibly electrochemicallyreducible redox system, and

[0024] RED₁ represents the radical of a reversibly electrochemicallyoxidizable redox system,

[0025] B represents a bridge member

[0026] c represents an integer from 0 to 5, and

[0027] a and b independently of one another represent an integer from 0to 5, preferably an integer from 0 to 3.

[0028] The electrochromic system preferably comprises at least oneelectrochromic substance of the formula (I) in which

[0029] Y represents OX₂ and Z represents RED₁ and Y and Z alternate intheir sequence.

[0030] With particular preference, the electrochromic system of theinvention comprises at least one electrochromic substance of the formula

OX₂—B—RED₁   (Ia),

OX₂—B—RED₁—B—OX₂   (Ib),

RED₁—B—OX₂—B—RED₁   (Ic), or

OX₂—(B—RED₁—B—OX₂)_(d)—B—RED₁   (Id),

[0031] in which

[0032] OX₂, RED₁ and B have the meaning indicated above and

[0033] d represents an integer from 1 to 5.

[0034] The electrochromic system of the invention preferably comprisesat least one anion type X⁻ which a) has a molar mass>200 g/mol,preferably>250 g/mol and/or b) has a cagelike structure, where X⁻ is thecounterion of OX₂ and/or is a constituent of an inert conductive salt.

[0035] Anions with cagelike structure means especially such anions,which are derived from carbaboranes, with very particular preferencedicarba-nido-undecarborates and dicarba-closo-dodecarborates.

[0036] Where OX₂ has no positive charge the anion type X⁻ that ispresent in accordance with the invention is a constituent of an inertconductive salt.

[0037] The anion type X⁻ present in the electrochromic system of theinvention may suitably be, in particular:

[0038] C₁₀- to C₂₅-alkanesulphonate, preferably C₁₃- toC₂₅-alkanesulphonate, C₃- to C₁₈-perfluoroalkanesulphonate, preferablyC₅- to C₁₈-perfluoroalkanesulphonate, C₁₃- to C₂₅-alkanoate,benzenesulphonate substituted by nitro, C₄- to C₂₅-alkyl, perfluoro-C₁-to C₈-alkyl, C₁- to C₁₂-alkoxycarbonyl or dichloro, naphthalene- orbiphenylsulphonate each of which is unsubstituted or substituted bynitro, cyano, hydroxyl, C₁- to C₂₅-alkyl, C₁- to C₁₂-alkoxy, amino, C₁-to C₁₂-alkoxycarbonyl or chloro, benzene-, naphthalene- orbiphenyldisulphonate each of which is unsubstituted or substituted bynitro, cyano, hydroxyl, C₁- to C₂₅-alkyl, C₁- to C₁₂-alkoxy, C₁- toC₁₂-alkoxycarbonyl or chloro, benzoate substituted by dinitro, C₆- toC₂₅-alkyl, C₄- to C₁₂-alkoxycarbonyl, benzoyl, chlorobenzoyl or toluoyl,or the anion of naphthalenedicarboxylic acid, diphenyl etherdisulphonate, tetraphenylborate, cyanotriphenylborate, tetra-C₃- toC₂₀-alkoxyborate, tetraphenoxyborate, 7,8- or7,9-dicarba-nido-undecaborate(1−) or (2−), each of which isunsubstituted or substituted on the B and/or C atoms by one or two C₁-to C₁₂-alkyl or phenyl groups, dodecahydrodicarbadodecaborate(2−) orB-C₁- to C₁₂-alkyl-C-phenyl-dodecahydrodicarbadodecaborate(1−).

[0039] With very particular preference, the electrochromic system of theinvention comprises at least one electrochromic substance of theformulae (Ia)-(Id)

[0040] in which

[0041] OX₂ represents the radical of a cathodically reducible substancewhich in its cyclic voltammogram, recorded in an inert solvent at roomtemperature, exhibits at least two chemically reversible reductionwaves, the first of these reduction waves leading to an increase in theabsorbance at at least one wavelength in the visible region of theelectromagnetic spectrum,

[0042] RED₁ represents the radical of an anodically reversiblyoxidizable substance which in its cyclic voltammogram, recorded in aninert solvent at room temperature, exhibits at least two chemicallyreversible oxidation waves, the first of these oxidation waves leadingto an increase in the absorbance at at least one wavelength in thevisible region of the electromagnetic spectrum, and

[0043] B represents a bridge.

[0044] Particular preference is given to an electrochromic system of theinvention which comprises at least one substance of the formula(Ia)-(Id) in which

[0045] OX₂ represents a radical of the formula

[0046] where

[0047] R² to R⁵, R⁸, R⁹, R¹⁶ to R¹⁹ independently of one another denoteC₁- to C₁₈-alkyl, C₂- to C₁₂-alkenyl, C₃- to C₇-cycloalkyl, C₇- toC₁₅-aralkyl or C₆- to C₁₀-aryl, or

[0048] R⁴ and R⁵ or R⁸ and R⁹ together form a —(CH₂)₂— or —(CH₂)₃—bridge,

[0049] R⁶, R⁷ and R²² to R²⁵ independently of one another denotehydrogen, C₁- to C₄-alkyl, C₁- to C₄-alkoxy, halogen, cyano, nitro orC₁- to C₄-alkoxycarbonyl, or

[0050] R²² and R²³ and/or R²⁴ and R²⁵ form a —CH═CH—CH═CH— bridge,

[0051] R¹⁰ and R¹¹, R¹² and R¹³, R¹⁴ and R¹⁵ independently of oneanother denote hydrogen or in pairs denote a —(CH₂)₂—, —(CH₂)₃— or—CH═CH— bridge,

[0052] R²⁰ and R²¹ independently of one another denote O, N—CN, C(CN)₂or N—C₆- to C₁₀-aryl,

[0053] R²⁶ denotes hydrogen, C₁- to C₄-alkyl, C₁- to C₄-alkoxy, halogen,cyano, nitro, C₁- to C₄-alkoxycarbonyl or C₆- to C₁₀-aryl,

[0054] R⁶⁹ to R⁷⁴ independently of one another denote hydrogen orC₁-C₆-alkyl, or

[0055] R⁶⁹; R¹² and/or R⁷⁰; R¹³ form a —CH═CH—CH═CH— bridge,

[0056] E¹ and E² independently of one another denote O, S, NR¹ orC(CH₃)₂, or

[0057] E¹ and E² together form an —N—(CH₂)₂—N— bridge,

[0058] R¹ denotes C₁- to C₁₈-alkyl, C₂- to C₁₂-alkenyl, C₄- toC₇-cycloalkyl, C₇- to C₁₅-aralkyl, C₆- to C₁₀-aryl,

[0059] Z¹ denotes a direct bond, —CH═CH—, —C(CH₃)═CH—, —C(CN)═CH—,—CCl═CCl—, —C(OH)═CH—, —CCl═CH—, —C≡C—, —CH═N—N═CH—, —C(CH₃)═N—N═C(CH₃)— or —CCl═N—N═CCl—,

[0060] Z² denotes —(CH₂)_(r)— or —CH₂—C₆H₄—CH₂—,

[0061] r denotes an integer from 1 to 10,

[0062] X⁻ represents an anion which is redox-inert under the conditionsand which a) has a molar mass>200 g/mol, preferably>250 g/mol and/or b)has a cagelike structure,

[0063] where the bond to the bridge B is via one of the radicals R²-R¹⁹,R²²-R²⁷ or, if E¹ or E² represents NR¹, is via R¹, and the radicalsmentioned in that case represent a direct bond,

[0064] RED₁ represents one of the following radicals

[0065] in which

[0066] R²⁸ to R³¹, R³⁴, R³⁵, R³⁸, R³⁹, R⁴⁶, R⁵³ and R⁵⁴ independently ofone another denote C₁- to C₁₈-alkyl, C₂- to C₁₂-alkenyl, C₃- toC₇-cycloalkyl, C₇- to C₁₅-aralkyl or C₆- to C₁₀-aryl, and R⁴⁶, R⁵³ andR⁵⁴ additionally denote hydrogen,

[0067] R³², R³³, R³⁶, R³⁷, R⁴⁰, R⁴¹, R⁴² to R⁴⁵, R⁴⁷, R⁴⁸, R⁴⁹ to R⁵²and R⁵⁵ to R⁵⁷ independently of one another denote hydrogen, C₁- toC₄-alkyl, C₁- to C₄-alkoxy, halogen, cyano, nitro, C₁- toC₄-alkoxycarbonyl or C₆- to C₁₀-aryl and R⁵⁷ and R⁵⁸ additionally denotean optionally benzo-fused aromatic or quasi-aromatic five- orsix-membered heterocyclic ring and R⁴⁸ additionally denotes NR⁷⁵R⁷⁶,

[0068] R⁴⁹ and R⁵⁰ and/or R⁵¹ and R⁵² form a —(CH₂)₃—, —(CH₂)₄—,—(CH₂)₅— or —CH═CH—CH═CH— bridge,

[0069] Z³ denotes a direct bond, a —CH═CH— or —N═N— bridge,

[0070] ═Z⁴═ denotes a direct double bond, a ═CH—CH═ or ═N—N═ bridge,

[0071] E³ to E⁵, E¹⁰ and E¹¹ independently of one another denote O, S,NR⁵⁹ or C(CH₃)₂, and E⁵ additionally denotes C═O or SO₂, or

[0072] E³ and E⁴ independently of one another denote —CH═CH—,

[0073] E⁶ to E⁹ independently of one another denote S, Se or NR⁵⁹,

[0074] R⁵⁹, R⁷⁵ and R⁷⁶ independently of one another denote C₁- toC₁₂-alkyl, C₂- to C₈-alkenyl, C₃- to C₇-cycloalkyl, C₇- to C₁₅-aralkylor C₆- to C₁₀-aryl, and R⁷⁵ additionally denotes hydrogen, or

[0075] R⁷⁵ and R⁷⁶ in the definition of NR⁷⁵R⁷⁶ form, together with theN atom to which they are attached, a five- or six-membered, saturatedring which can contain further heteroatoms,

[0076] R⁶¹ to R⁶⁸ independently of one another denote hydrogen, C₁- toC₆-alkyl, C₁- to C₄-alkoxy, cyano, C₁- to C₄-alkoxycarbonyl or C₆- toC₁₀-aryl, or

[0077] R⁶¹; R⁶² and R⁶⁷; R⁶⁸ independently of one another, together forma —(CH₂)₃—, —(CH₂)₄— or —CH═CH—CH═CH— bridge,

[0078] v denotes an integer between 0 and 10,

[0079] the bond to the bridge B being via one of the radicals R²⁸-R⁵⁸,R⁶¹, R⁶², R⁶⁷, R⁶⁸ or, if one of the radicals E³—E¹¹ represents NR⁵⁹, isvia R⁵⁹ and the abovementioned radicals in that case represent a directbond, and

[0080] B represents a bridge of the formula —(CH₂)_(n)— or —[Y¹_(s)(CH₂)_(m)—Y²]_(o)—(CH₂)_(p)—Y³ _(q)—, each of which is unsubstitutedor substituted by C₁- to C₄-alkoxy, halogen or phenyl,

[0081] Y¹ to Y³ independently of one another represent O, S, NR⁶⁰, COO,CONH, NHCONH, cyclopentanediyl, cyclohexanediyl, phenylene ornaphthylene,

[0082] R⁶⁰ denotes C₁- to C₆-alkyl, C₂- to C₆-alkenyl, C₄- toC₇-cycloalkyl, C₇- to C₁₅-aralkyl or C₆- to C₁₀-aryl,

[0083] n denotes an integer from 1 to 12,

[0084] m and p independently of one another denote an integer from 0 to8,

[0085] o denotes an integer from 0 to 6, and

[0086] q and s independently of one another denote 0 or 1,

[0087] and, if OX₂ has no positive charge, there is at least oneconductive salt present which comprises the abovementioned anion X⁻.

[0088] Very particular preference is given to an electrochromic systemof the invention which comprises at least one substance of the formula(Ia)-(Id)

[0089] in which

[0090] OX₂ represents a radical of the formula (II), (III), (IV) or (V)

[0091] where

[0092] R², R³, R⁴, R⁵, R⁸ and R⁹ independently of one another representC₁- to C₁₂-alkyl, C₂- to C₈-alkenyl, C₅- to C₇-cycloalkyl, C₇- toC₁₅-aralkyl or C₆- to C₁₀-aryl,

[0093] R⁶ and R⁷ independently of one another represent hydrogen,methyl, ethyl, methoxy, fluoro, chloro, bromo, cyano, nitro,methoxycarbonyl or ethoxycarbonyl,

[0094] R¹⁰, R¹¹; R¹², R¹³ and R¹⁴, R¹⁵ independently of one anotherrepresent hydrogen or, if Z¹ denotes a direct bond, in each casetogether represent a —(CH₂)₂—, —(CH₂)₃— or —CH═CH— bridge,

[0095] or

[0096] R⁴, R⁵ and R⁸, R⁹ independently of one another in pairs togetherrepresent a —(CH₂)₂— or —(CH₂)₃— bridge if Z¹ denotes a direct bond,

[0097] R⁶⁹ to R⁷⁴ independently of one another denote hydrogen orC₁-C₄-alkyl,

[0098] E¹ and E² are identical and represent O, S, NR¹ or C(CH₃)₂ ortogether form an —N—(CH₂)₂—N— bridge,

[0099] R¹ represents C₁- to C₁₂-alkyl, C₂- to C₄-alkenyl, C₅- toC₇-cycloalkyl, C₇- to C₁₅-aralkyl or C₆- to C₁₀-aryl,

[0100] Z¹ represents a direct bond, —CH═CH—, —C(CH₃)═CH—, —C(CN)═CH—,—C≡C— or —CH═N—N═CH—,

[0101] Z² represents —(CH)_(r)— or —CH₂—C₆H₄—CH₂—,

[0102] r represents an integer between 1 and 6,

[0103] X⁻ represents C₁₀- to C₂₅-alkanesulphonate, preferably C₁₃- toC₂₅-alkane-sulphonate, C₃- to C₁₈-perfluoroalkanesulphonate, preferablyC₅- to C₁₈-perfluoroalkanesulphonate, C₁₃- to C₂₅-alkanoate,benzenesulphonate substituted by nitro, C₄- to C₂₅-alkyl, perfluoro-C₁-to C₈-alkyl, C₁- to C₁₂-alkoxycarbonyl or dichloro, naphthalene- orbiphenylsulphonate each of which is unsubstituted or substituted bynitro, cyano, hydroxyl, C₁- to C₂₅-alkyl, C₁- to C₁₂-alkoxy, amino, C₁-to C₁₂-alkoxycarbonyl or chloro, benzene-, naphthalene- orbiphenyldisulphonate each of which is unsubstituted or substituted bynitro, cyano, hydroxyl, C₁- to C₂₅-alkyl, C₁- to C₁₂-alkoxy, C₁- toC₁₂-alkoxycarbonyl or chloro, benzoate substituted by dinitro, C₆- toC₂₅-alkyl, C₄- to C₁₂-alkoxycarbonyl, benzoyl, chlorobenzoyl or toluoyl,or the anion of naphthalenedicarboxylic acid, diphenyl etherdisulphonate, tetraphenylborate, cyanotriphenylborate, tetra-C₃- toC₂₀-alkoxyborate, tetraphenoxyborate, 7,8- or7,9-dicarba-nido-undecaborate(1−) or (2−), each of which isunsubstituted or substituted on the B and/or C atoms by one or two C₁-to C₁₂-alkyl or phenyl groups, dodecahydrodicarbadodecaborate(2−) orB-C₁- to C₁₂-alkyl-C-phenyl-dodecahydrodicarbadodecaborate(1−), where inthe case of polyvalent anions such as naphthalenedisulphonate X⁻represents one equivalent of this anion,

[0104] where the bond to the bridge B is via one of the radicals R²-R¹¹or, if E¹ or E² represents NR¹, is via R¹, and the abovementionedradicals in that case represent a direct bond,

[0105] RED₁ represents a radical of the formula (X), (XI), (XII),(XIlI), (XVI), (XVII), (XVIII) or (XX),

[0106] where

[0107] R²⁸ to R³¹, R³⁴, R³⁵, R³⁸, R³⁹, R⁴⁶, R⁵³ and R⁵⁴ independently ofone another denote C₁- to C₁₂-alkyl, C₂- to C₈-alkenyl, C₅- toC₇-cycloalkyl, C₇- to C₁₅-aralkyl or C₆- to C₁₀-aryl and

[0108] R⁴⁶, R⁵³ and R⁵⁴ additionally denote hydrogen,

[0109] R³², R³³, R³⁶, R³⁷, R⁴⁰, R⁴¹, R⁴⁷ to R⁵², R⁵⁵ and R⁵⁶independently of one another denote hydrogen, methyl, ethyl, methoxy,ethoxy, fluoro, chloro, bromo, cyano, nitro, methoxycarbonyl,ethoxycarbonyl or phenyl, and

[0110] R⁵⁷ and R⁵⁸ additionally denote 2- or 4-pyridyl, and

[0111] R⁴⁸ additionally denotes NR⁷⁵R⁷⁶,

[0112] Z³ denotes a direct bond, a —CH═CH— or —N═N— bridge,

[0113] ═Z⁴═ denotes a direct double bond, a ═CH—CH═ or ═N—N═ bridge,

[0114] E³ to E⁵, E¹⁰ and E¹¹, independently of one another denote O, S,NR⁵⁹ or C(CH₃)₂, but E³ and E⁴ have the same meaning,

[0115] E⁶ to E⁹ are identical to one another and denote S, Se or NR⁵⁹,and

[0116] E⁵ additionally denotes C═O,

[0117] E⁶ represents NR⁵⁹, where R⁵⁹ denotes a direct bond to the bridgeB, and

[0118] E⁷ to E⁹ possess the meaning indicated above, but need not beidentical to one another,

[0119] R⁵⁹, R⁷⁵ and R⁷⁶ independently of one another denote C₁- toC₁₂-alkyl, C₂- to C₈-alkenyl, C₅- to C₇-cycloalkyl, C₇- to C₁₅-aralkylor C₆- to C₁₀-aryl, and R⁷⁵ additionally denotes hydrogen, or

[0120] R⁷⁵ and R⁷⁶ in the definition NR⁷⁵R⁷⁶ denote, together with the Natom to which they are attached, pyrrolidino, piperidino or morpholino,

[0121] R⁶¹, R⁶² and R⁶⁷, R⁶⁸ independently of one another representhydrogen, C₁- to C₄-alkyl, methoxycarbonyl, ethoxycarbonyl or phenyl, orin pairs together represent a —(CH₂)₃— or —(CH₂)₄— bridge,

[0122] R⁶³ to R⁶⁶ represent hydrogen, and

[0123] v represents an integer from 1 to 6,

[0124] where the bond to the bridge B is via one of the radicalsR²⁸-R⁴¹, R⁴⁶-R⁵⁶, R⁶¹, R⁶², R⁶⁷, R⁶⁸ or, if one of the radicals E³-E¹¹represents NR⁵⁹, is via R⁵⁹, and the abovementioned radicals in thatcase represent a direct bond,

[0125] B represents a bridge of the formulae —(CH₂)_(n)—,—(CH₂)_(m)—O—(CH₂)_(p)—, —(CH)_(m)—NR⁶⁰—(CH₂)_(p)—,—(CH₂)_(m)—C₆H₄—(CH₂)_(p)—, —[O—(CH₂)_(p)]_(o)—O—,—[NR⁶⁰—(CH₂)_(p)]_(o)—NR⁶⁰—, —[C₆H₄—(CH₂)_(p)]_(o)—C₆H₄—,—(CH₂)_(m)—OCO—C₆H₄—COO—(CH₂)_(p)—,—(CH₂)_(m)—NHCO—C₆H₄—CONH—(CH₂)_(p)—,—(CH₂)_(m)—NHCONH—C₆H₄NHCONH—(CH₂)_(p)—,—(CH₂)_(m)—OCO—(CH₂)_(t)—COO—(CH₂)—,—(CH₂)_(m)—NHCO—(CH₂)_(t)—CONH—(CH)_(p)—,—(CH₂)_(m)—NHCONH—(CH₂)_(t)—NHCONH—(CH₂)_(p)—,

[0126] R⁶⁰ represents methyl, ethyl, benzyl or phenyl,

[0127] n represents an integer from 1 to 10,

[0128] m and p independently of one another represent an integer from 0to 4,

[0129] o represents an integer from 0 to 2, and

[0130] t represents an integer from 1 to 6.

[0131] Especial preference is given to an electrochromic system of theinvention which comprises at least one substance of the formula(Ia)-(Id)

[0132] in which

[0133] OX₂ represents a radical of the formula (II), (IV) or (V)

[0134] in which

[0135] R², R⁴ and R⁸ represent a direct bond to the bridge B,

[0136] R³, R⁵ and R⁹ independently of one another represent methyl,ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, benzyl or phenyl, orin the case of the formula Ic or Id likewise represent a direct bond tothe bridge B,

[0137] R⁶ and R⁷ are identical and represent hydrogen, methyl, methoxy,chloro, cyano or methoxycarbonyl,

[0138] R¹⁰, R¹¹; R¹², R¹³ and R¹⁴, R¹⁵ independently of one anotherrepresent hydrogen or, if Z¹ denotes a direct bond, represent, in eachcase in pairs together, a —CH═CH— bridge,

[0139] R⁶⁹ to R⁷² are identical and denote hydrogen, methyl or ethyl,

[0140] R⁷³ and R⁷⁴ denote hydrogen,

[0141] E¹ and E² are identical and represent O or S,

[0142] Z¹ represents a direct bond or —CH═CH—,

[0143] X⁻ represents C₁₅- to C₂₂-alkanesulphonate, C₅- toC₁₂-perfluoroalkanesulphonate, nitrobenzenesulphonate,dinitrobenzenesulphonate, mono- or bis-C₄- toC₁₂-alkylbenzenesulphonate, dichlorobenzenesulphonate,naphthalenesulphonate, nitronaphthalenesulphonate,dinitronaphthalenesulphonate, mono- or bis-C₃- toC₁₂-alkylnaphthalenesulphonate, hydroxynapththalenesulphonate,aminonaphthalenesulphonate, biphenyl-sulphonate, benzenedisulphonate,nitrobenzenedisulphonate, C₄- to C₁₂- alkylbenzenedisulphonate,naphthalenedisulphonate, nitronaphthalenedisulphonate, C₄- toC₁₂-alkylnaphthalenedisulphonate, biphenyldisulphonate, dinitrobenzoate,mono- or bis-C₈- to C₁₂-alkylbenzoate, C₆- toC₁₂-alkoxycarbonylbenzoate, benzylbenzoate, toluoylbenzoate, the anionof naphthalenedicarboxylic acid, cyanotriphenylborate, tetra-C₃- toC₁₂-alkoxyborate, tetraphenoxyborate, 7,8- or7,9-dicarba-nido-undecaborate(1−) or (2−) each of which is unsubstitutedor substituted on the B and/or C atoms by one or two methyl, ethyl,butyl or phenyl groups, dodecahydrodicarbadodecaborate(2−) orB-methyl-C-phenyl-dodecahydro-dicarbadodecaborate(1−), where in the caseof polyvalent anions such as naphthalenedisulphonate X⁻ represents oneequivalent of this anion,

[0144] RED₁ represents a radical of the formula (X), (XII), (XIII),(XVI) or (XVII),

[0145] R²⁸, R³⁴, R³⁸, R⁴⁶ and R⁴⁹ represent a direct bond to the bridgeB,

[0146] R²⁹ to R³¹, R³⁵ and R³⁹ independently of one another representmethyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, benzyl orphenyl, or, in the case of the formula Ib or Id, R³⁰, R³⁵ and R³⁹likewise represent the direct bond to the bridge B,

[0147] R³², R⁴⁷ and R⁴⁸ represent hydrogen,

[0148] R³⁶, R³⁷, R⁴⁰, R⁴¹ and R⁵⁰ to R⁵² independently of one anotherrepresent hydrogen, methyl, methoxy, chloro, cyano, methoxycarbonyl orphenyl, or, in the case of the formula Ib or Id, R⁵¹ likewise representsa direct bond to the bridge B,

[0149] Z³ represents a direct bond, a —CH═CH— or —N═N— bridge,

[0150] ═Z⁴═ represents a direct double bond, a ═CH—CH═ or ═N—N═ bridge,

[0151] E³ to E⁵ independently of one another represent O, S or NR⁵⁹, butE³ and E⁴ have the same meaning,

[0152] E⁶ to E⁹ are identical to one another and represent S, Se orNR⁵⁹,

[0153] R⁵⁹ represents methyl, ethyl, propyl, butyl, pentyl, hexyl,heptyl, octyl, benzyl or phenyl, or, in the case of the formula XVI inIb or Id, likewise represents a direct bond to the bridge B,

[0154] B represents a bridge of the formulae —(CH₂)_(n)—,—(CH₂)_(m)—O—(CH₂)_(p)—, —(CH₂)_(m)—NR⁶⁰—(CH₂)_(p)—, —(CH₂)_(m)—C₆H₄—(CH₂)_(p)—, —O—(CH₂)_(p)—O—, —NR⁶⁰—(CH₂)_(p)—NR⁶⁰—,—(CH₂)_(m)—OCO—C₆H₄—COO—(CH₂)_(p)—,—(CH₂)_(m)—NHCO—C₆H₄—CONH—(CH₂)_(p)—,—(CH₂)_(m)—NHCONH—C₆H₄—NHCONH—(CH₂)_(p)—,—(CH₂)_(m)—OCO—(CH₂)_(t)—COO—(CH₂)_(p)—,—(CH₂)_(m)—NHCO—(CH₂)_(t)—CONH—(CH₂)_(p)—,—(CH₂)_(m)—NHCONH—(CH₂)_(t)—NHCONH—(CH₂)_(p)—,

[0155] R⁶⁰ represents methyl,

[0156] n represents an integer from 1 to 10,

[0157] m and p are identical and represent an integer from 0 to 2, and

[0158] t represents an integer from 1 to 6.

[0159] Very particular preference is given to an electrochromic systemof the invention which comprises at least one substance of the formula(Ia) corresponding to one of the formulae

[0160] or at least one substance of the formula (Ib) corresponding toone of the formulae

[0161] or at least one substance of the formula (Ic) corresponding toone of the formulae

[0162] in which

[0163] R³, R⁵, R³⁵ and R³⁹ independently of one another representmethyl, ethyl, propyl, butyl, pentyl, hexyl or benzyl,

[0164] R⁶, R⁷ and R³⁶, R³⁷ in pairs are identical and representhydrogen, methyl, methoxy, chloro, cyano or methoxycarbonyl,

[0165] R¹² and R¹³ represent hydrogen or, if Z¹ denotes a direct bond,together represent a —CH═CH— bridge,

[0166] R⁶⁹ to R⁷² are identical and represent hydrogen or methyl,

[0167] E¹ and E² are identical and represent O or S,

[0168] Z¹ represents a direct bond or —CH═CH—,

[0169] R³², R⁴⁷ and R⁴⁸ represent hydrogen,

[0170] E³ to E⁵ independently of one another represent O, S or NR⁵⁹, butE³ and E⁴ are identical,

[0171] R²⁹ to R³¹ and and R⁵⁹ independently of one another representmethyl, ethyl, propyl, butyl, pentyl, hexyl or benzyl, where R²⁹ to R³¹are preferably identical,

[0172] R⁴⁰ and R⁴¹ are identical and represent hydrogen, methyl, ethyl,propyl, butyl or phenyl,

[0173] Z³ represents a direct bond, —CH═CH— or —N═N—,

[0174] R⁵⁰ to R⁵² independently of one another represent hydrogen,methyl, methoxy, chloro, cyano, methoxycarbonyl, ethoxycarbonyl orphenyl, but are preferably identical,

[0175] E⁶ to E⁹ are identical to one another and represent S, Se orNR⁵⁹,

[0176] Z⁴ represents a direct double bond, a ═CH—CH═ or ═N—N═bridge,

[0177] m represents an integer from 1 to 5,

[0178] u represents 0 or 1, and

[0179] X⁻ represents C₁₅- to C₂₀-alkanesulphonate, C₅- toC₈-perfluoroalkanesulphonate, mono- or dibutylbenzenesulphonate, mono-or di-tert-butylbenzenesulphonate, octylbenzenesulphonate,dodecylbenzenesulphonate, naphthalenesulphonate, biphenylsulphonate,nitrobenzenedisulphonate, naphthalenedisulphonate,dibutylnaphthalenesulphonate, biphenyldisulphonate, benzoylbenzoate,cyanotriphenylborate, tetra-C₃- to C₈-alkoxyborate, tetraphenoxyborate,7,8- or 7,9-dicarba-nido-undecaborate(1−) or (2−) ordodecahydro-dicarbadodecaborate(2−) where in the case of polyvalentanions such as naphthalenedisulphonate X⁻ represents one equivalent ofthis anion.

[0180] In the abovementioned definitions of substituents alkyl radicals,including modified versions such as alkoxy or aralkyl radicals, forexample, are preferably those having 1 to 12 C atoms, especially having1 to 8 C atoms, unless indicated otherwise. They can be straight-chainor branched and can if desired carry further substituents such as, forexample, C₁- to C₄-alkoxy, fluoro, chloro, hydroxyl, cyano, C₁- toC₄-alkoxycarbonyl or COOH

[0181] Cycloalkyl radicals are preferably those having 3 to 7 C atoms,especially 5 or 6 C atoms.

[0182] Alkenyl radicals are preferably those having 2 to 8 C atoms,especially 2 to 4 C atoms.

[0183] Aryl radicals, including those in aralkyl radicals, arepreferably phenyl or naphthyl radicals, especially phenyl radicals. Theycan be substituted by 1 to 3 of the following radicals. C₁- to C₆-alkyl,C₁- to C₆-alkoxy, fluoro, chloro, bromo, cyano, hydroxyl, C₁- toC₆-alkoxycarbonyl or nitro. Two adjacent radicals can also form a ring,

[0184] The compounds of the formula (I) are known in principle from thenonprior-published German Application No. 19605451.6 and can be preparedas described therein.

[0185] Compounds of the formula (I), which as counterion contain theabove-defined anion X⁻ are novel and are likewise a subject of thepresent invention.

[0186] Owing to their synthesis, the electrochromic compounds obtainedin accordance with WO 97/30134 of the formula (I), do not carry anyanions X⁻ of the invention. These anions X⁻ have to be introduced bymeans of anion exchange. This exchange can take place, for example, insolvents in which the compounds of the formula (I) with the anionsoriginating from their synthesis are of moderate to good solubility butin which the compounds of the formula (l) with the anions of theinvention are of poor solubility. The compounds of the formula (I) withthe anions originating from their synthesis are then introduced,together with salts of the anions of the invention, for example thealkali metal salts or tetraalkyl-ammonium salts listed below underconductive salts, into such solvents, and these mixtures are stirred atfrom room temperature to the reflux temperature of the solvent, thedesired compounds of the formula (I) with the anions of the inventionbeing precipitated and being filtered off with suction. Examples ofsuitable solvents are alcohols such as methanol, ethanol; water;nitrites such as acetonitrile, or mixtures thereof.

[0187] Another process involves operating in a two-phase mixture, inwhich case the compounds of the formula (I) with the anions originatingfrom their synthesis and the alkali metal salts or tetraalkylammoniumsalts of the anions X⁻ of the invention should be at least partlysoluble in one solvent while the compounds of the formula (I) with theanions X⁻ of the invention should be readily soluble in the othersolvent. This mixture is then stirred at from room temperature to thereflux temperature of the solvent mixture, and is separated. Removal ofthe second solvent by distillation gives the compounds of the formula(I) with the anions X⁻ of the invention Examples of suitable pairs ofsolvents are water/toluene, water/methylene chloride and water/butanone.

[0188] A third possibility is the use of ion exchangers.

[0189] The electrochromic system of the invention preferably comprisesat least one solvent, resulting in an electrochromic fluid which islikewise a subject of the present invention.

[0190] Suitable solvents are all solvents which are redox-inert at thechosen voltages and which cannot give off electrophiles or nucleophilesor themselves react as sufficiently strong electrophiles or nucleophilesand so could react with the coloured ionic free radicals. Examples arepropylene carbonate, γ-butyrolactone, acetonitrile, propionitrile,glutaronitrile, methylglutaronitrile, 3,3′-oxydipropionitrile,hydroxypropionitrile, dimethylformamide, N-methylpyrrolidone,sulpholane, 3-methylsulpholane or mixtures thereof. Preference is givento propylene carbonate and to mixtures thereof with glutaronitrile or3-methylsulpholane.

[0191] The electrochromic fluid of the invention can include at leastone inert conductive salt. It must include a conductive salt if OX₂ isnot cationic.

[0192] Suitable inert conductive salts are lithium, sodium andtetraalkylammonium salts, especially the latter. The alkyl groups canhave between 1 and 18 C atoms and can be identical or different.Tetrabutylammonium is preferred. Anions of these salts are theabovementioned anions X⁻ in their general, particular or very particulardefinitions.

[0193] The conductive salts are preferably employed in the range from 0to 1 molar.

[0194] Further possible additives to the electrochromic fluid arethickeners, in order to control the viscosity of the fluid. This may beimportant for controlling the rate of fade after switching off thecurrent.

[0195] Suitable thickeners are all compounds usual for these purposes,such as polyacrylate, polymethacrylate (Luctite L®), polycarbonate andpolyurethane, for example

[0196] The electrochromic fluid can also be in gel form.

[0197] Other suitable additives for the electrochromic fluid are UVabsorbers to improve the lightfastness. Examples are Uvinul® 3000(2,4-dihydroxybenzophenone, BASF), SANDUVOR® 3035(2-hydroxy-4-n-octyloxybenzophenone, Clariant), Tinuvin® 571(2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol, Ciba), Cyasorb 24®(2,2′-dihydroxy-4-methoxybenzophenone, American Cyanamid Company),UVULA® 3035 (ethyl 2-cyano-3,3-diphenylacrylate, BASF), Uvinul® 3039(2-ethylhexyl 2-cyano-3,3-diphenylacrylate, BASF), UVINUL® 3088(2-ethylhexyl p-methoxycinnamate, BASF), and CHIMASSORB®90(2-hydroxy-4methoxy-benzophenone, Ciba).

[0198] The UV absorbers are employed in the range from 0.01 to 2 mol/l,preferably from 0.04 to 1 mol/l.

[0199] The electrochromic fluid of the invention comprises thesubstances of the formula (I), especially of the formulae (Ia) to (Id),in each case in a concentration of at least 10⁻⁴ mol/l, preferably from0.001 to 1 mol/l. It is also possible to employ mixtures of two or moreelectrochromic substances of the formula (I).

[0200] The electrochromic fluids of the invention are eminently suitableas a constituent of an electrochromic device. A further subject of thepresent invention, accordingly, are electrochromic devices comprising anelectrochromic fluid of the invention. The design of an electrochromicdevice, which may be configured, for example, as a window pane, carsunroof, rearview car mirror or display, is known in principle. Theelectrochromic device of the invention consists of two transparent glassor plastic plates facing one another, of which one may be mirrored, andwhose facing sides have an electroconductive coating of, for example,indium tin oxide (ITO) and between which there is located theelectrochromic fluid of the invention. Other suitable conductivematerials are antimony-doped tin oxide, fluorine-doped tin oxide,antimony-doped zinc oxide, aluminium-doped zinc oxide, tin oxid; andalso conductive organic polymers, such as unsubstituted or substitutedpolythienyls, polypyrroles, polyanilines, polyacetylene. If one of theplates is mirrored, it can also be used as a conductive layer. Thedistance between the two plates is generally 0.005-2 mm, preferably0.02-0.5 mm. The desired distance between the plates is generallyestablished by means of a sealing ring.

[0201] In the case where the electrochromic device is an electrochromicdisplay device, at least one of the two conductive layers, or both, aresubdivided into electrically separate segments that are contactedindividually.

[0202] Alternatively, it is possible for only one of the two plates tocarry the conductive coating and to be subdivided into segments. Theseparation of the segments can be effected, for example, by means ofmechanical removal of the conductive layer, for example by scoring,scratching, scraping or milling, or chemically, for example by etchingusing, for instance, a solution of FeCl₂ and SnCl₂ in hydrochloric acid.This removal of the conductive layer can be locally controlled by meansof masks, for example photoresistant masks. Also possible, however, isthe production of the electrically separate segments by means ofcontrolled—for example, by means of masks—application—for example,sputtering or printing—of the conductive layer. The contacting of thesegments takes place, for example, by means of fine strips of conductivematerial, by means of which the segment is brought into electricallyconducting communication with a contact at the edge of theelectrochromic device. These fine contact strips can consist either ofthe same material as the conductive layer itself and can be prepared,for example, along with said layer at the same time as it is subdividedinto segments as described above, or alternatively, in order to improvethe conductivity, they can consist of a different material, such as finemetallic conductors made, for example, from copper or silver. Acombination of metallic material and the material of the conductivecoating is a further possibility. These metallic conductors may, forexample, be applied, e.g. bonded, in fine wire form, or else may beprinted on. All of these above-described techniques are common knowledgefrom the production of liquid-crystal displays (LCD).

[0203] The displays can be viewed in transmitted light or elsereflectively via a mirror coating.

[0204] The two plates are laid atop one another with the conductivelycoated and segmented sides facing, separated by means, for example, of asealing ring, and are bonded to one another at the edge. The sealingring may be made, for example, of plastic or thin glass or anothermaterial which is inert with respect to the electrochromic fluid. Thedistance between the plates can also, however, be established by meansof different spacers, for example by means of small plastic or glassbeads or particular fractions of sand, in which case these spacers areapplied together with the adhesive and then together form the sealingring. The sealing ring includes one or two cutouts which are used tofill the electrochromic device.

[0205] The distance between the two plates lies between 0.005 and 2 mm,and is preferably from 0.02 to 0.5 mm. In the case of large-surface-areadisplay devices, especially those made of plastic, it may beadvantageous to use spacers, for example plastic beads of equal diameterdistributed over the area of the display device, to keep the distancebetween the plates constant.

[0206] This display device is filled with an electrochromic fluid viathe apertures in the sealing ring, an operation which must be carriedout at all times with exclusion of moisture and oxygen. Filling can becarried out, for example, by means of fine cannulas or else by thevacuum filling technique, in which the device and the fluid are placedinto a shallow dish and introduced into an evacuable container. Thiscontainer is evacuated. Then the display device, which includes only onefilling aperture, is dipped with said aperture into the liquid. When thevacuum is removed, the liquid is then forced into the display device.

[0207] When such electrochromic devices are placed upright in theswitched-on state, there is—even after a number of hours or days—noseparation of the colours of the coloured species formed at the anodeand cathode, e.g. OX¹-B-RED₁ and RED₂-B-OX₂. The devices are uniform incolour, show no spotting or striping, and fade rapidly and uniformlyafter the current is switched off. If, on the other hand, use is made ofelectrochromic compounds of the formula (I) whose anion is not an anionX⁻ of the invention, such as tetrafluoroborate, then after just a shorttime, for example after 1 hour, there is a marked colour separation inthe upright electrochromic device. For example, there is a blue stripeat the top end and a yellow stripe at the bottom end, while in themiddle the expected mixed colour, green, is observed. After the voltageis switched off only the middle zone fades rapidly, whereas the upperand lower zones remain coloured for a relatively long time, for examplefor several hours. The same observation is made in the case ofelectrochromic compounds of the formula (I) whose OX₂ is not cationicand hence there is no anion, and yet which are employed in anelectrochromic fluid whose conductive salt is not an anion of theinvention, e.g. tetrafluoroborate.

[0208] In the case of electrochromic display devices, for examplesegmented displays, when the electrochromic compounds or fluids of theinvention are used, no colour separation within the segment is likewisefound, even in the case of long periods of operation in the uprightposition of the device, and there is rapid and complete erasure afterthe current is switched off, whereas the use of the abovementionedelectrochromic substances or fluids not of the invention leads to colourseparation and to a very slow erasure of these separated colour regions.Specifically in the case of display devices it is a frequent occurrencethat individual segments are switched on for a relatively long periodand yet are required to fade rapidly when there is a change in theinformation to be displayed. The electrochromic compounds and liquids ofthe invention show significant advantages here over those which compriseanions not of the invention.

[0209] The self-erasing single-cell electrochromic device of theinvention can in addition to the above-described electrochromicsubstances of the formulae (I), especially of the formulae (Ia) to (Id),also include other such substances, as are described, for example, inU.S. Pat. No. 4,902,108, Topics in Current Chemistry, Vol. 92, pp. 1-44(1980) and Angew. Chem. 90, 927 (1978). Such electrochromic substanceshail, for example, from the groups indicated above, under the formulae(II) to (XX), in which case none of the radicals listed is able topossess the definition “direct bond to the bridge B”. Examples of othersuitable electrochromic substances are tetrazolinium salts or salts orcomplexes of metal ions, e.g. [Fe(C₅H₅)₂]^(0/1+). The admixture of suchredox systems may, for example, be advantageous in order to correct thecolour in the case of the electrochromic device of the invention, forexample of the display, in the switched-on state or to render the saidcolour more intense.

[0210] The anions of such electrochromic co-components are intended tohave the definition of X⁻ in its abovementioned general, particular andvery particular definition.

EXAMPLES Example 1

[0211] Preparing an electrochromic substance of the formula (I)

[0212] a) 5.0 g of 4,4′-bipyridyl were dissolved in 30 ml of ananhydrous acetonitrile at 50° C. At this temperature, 2.7 g of benzylbromide were added dropwise over the course of 50 minutes. After 3 h at50° C. the mixture was cooled and the pale yellow precipitate wasfiltered off with suction. It was washed with 60 ml of toluene and driedin vacuo. This gave 3.9 g (75% of theory) of the product of the formula

[0213] b) 10.1 g of phenothliazine were dissolved at room temperature in60 ml of anhydrous N-methylpyrrolidone under an N₂ atmosphere. 5.9 g ofpotassium tert-butylate were added. Heating to 30° C. gave an orangesuspension which was stirred at 30° C. for 30 minutes. Then 54 g of1,4-dibromobutane were added in one portion. Upon this addition thetemperature rose to 53° C. The mixture was heated to 70° C. over 45minutes, held at this temperature for 15 minutes and then cooled. Thelight brown suspension was introduced into 1 l of water. It wassubjected to extraction with 3×200 ml of toluene and the extract waswashed with 5×200 ml of water, dried over sodium sulphate andconcentrated on a rotary evaporator. The oily residue was dissolved in400 ml of hexane, insoluble material was removed by filtration, and theremaining solution was concentrated again. The excess 1,4-dibromobutanewas then distilled off at from 0.1 to 0.5 mbar. This gave 9.6 g (57% oftheory) of a reddish yellow, viscous oil of the formula

[0214] c) 3.7 g of the phenothiazine of the formula (LXV) were dissolvedat room temperature in 10 ml of anhydrous N-methylpyrrolidone under anN₂ atmosphere. 1.8 g of the dipyridinium salt of the formula (LXIV) wereadded. The suspension was heated to 80° C. over the course of 1 h andheld at this temperature for a total of 13 h. During this time, thesuspension became increasingly thicker. After the suspension had cooledto room temperature, it was filtered with suction and the solid productwas washed with 5 ml of N-methylpyrrolidone. The hygroscopic crudeproduct of the to formula

[0215] with X⁻=Br⁻ was dissolved in 7 ml of methanol and the solutionwas filtered. 3.0 g of sodium cyanotriphenylborate were sprinkled intothe filtrate over the course of 2 h. Slowly, precipitation came about,and was brought to completion over the course of 18 h of stirring atroom temperature. Finally, the precipitate was filtered off withsuction, washed with methanol until the runoff was colourless, and thendried in vacuo. This gave 0.5 g (13% of theory) of pale bluish powder ofthe formula (LXVI) with X⁻=NC—B(C₆H₅)₃ ⁻.

[0216] In an electrochromic device in accordance with Example 29-30 ablue-violet coloration with λ_(max)=517 and 606 nm was obtained

Example 2

[0217] a) 9.2 g of phenazine were suspended in 60 ml of anhydroustetrahydrofuran under a nitrogen atmosphere. 30.8 ml of 20% strength byweight phenyllithium solution in 7:3 cyclohexane/diethyl ether wereadded dropwise over the course of 15 minutes, during which thetemperature was held at max. 35° C. The solution was subsequentlystirred at room temperature for 30 minutes.

[0218] At 15° C., 30.2 ml of 1,4-dibromobutane were added in oneportion. Upon this addition the temperature rose to 38° C. After 6 h atroom temperature, 200 ml of water were added and the pH was adjusted to7.0. The organic phase was separated off, washed three times with 100 mlof water each time and concentrated in vacuo. Finally, excess1,4-dibromobutane was distilled off under a pressure of 0.2 mbar. Theoily residue was dissolved hot in 400 ml of ethanol. The productprecipitated on cooling was filtered off with suction, washed withethanol and hexane and dried. This gave 8.0 g (41% of theory) of a paleyellow powder of the 9,10-dihydrophenazine of the formula

[0219] b) 7.5 g of the 9,10-dihydrophenazine of the formula (LXVII) froma) and 6.1 g of 4,4′-bipyridyl were stirred in 100 ml of acetonitrile at70° C. under a nitrogen atmosphere for 24 h. After cooling, the mixturewas filtered with suction and the solid product was washed with 50 ml ofacetone. Drying gave 6.3 g (60% of theory) of the salt of the formula

[0220] c) 6.1 g of the salt obtained in b) were stirred in 70 ml ofN-methyl-2-pyrrolidone together with 2.7 ml of benzyl bromide at 70° C.under a nitrogen atmosphere for 7 h. After cooling, the mixture wasdiluted with 150 ml of toluene and the precipitated product was filteredoff with suction. It was washed thoroughly with 150 ml of toluene and500 ml of hexane and dried. This gave 5.5 g (69% of theory) of thedipyridinium salt of the formula

[0221] where X⁻=Br⁻.

[0222] d) 4.0 g of this product from c) were introduced under a nitrogenatmosphere into a two-phase mixture comprising 70 ml of water and 70 mlof toluene. 3.6 g of sodium dodecylbenzenesulphonate were added. Themixture was stirred at 50° C. for 2 h and cooled. During this time, theinitial cloudy mixture became a clear two-phase system. The toluenephase was separated off and concentrated to dryness in vacuo. This gave6.7 g of a sticky, pale greenish product of the formula (LXIX) withX⁻=C₁₂H₂₅—C₆H₄—SO₃ ⁻.

[0223] In an electrochromic device in accordance with Example 29-31 agreenish blue coloration with λ_(max)=466 and 407 nm was obtained

Example 2a Comparative Example

[0224] 4.0 g of this product from Example 2 c) were dissolved at 65° C.in 100 ml of methanol under a nitrogen atmosphere. 7.4 g oftetrabutylammonium tetrafluoroborate were sprinkled in over the courseof 5 minutes. Precipitation occurred. After 5 minutes at 65° C. themixture was cooled and the precipitate was filtered off with suction,washed with 200 ml of methanol and 50 ml of hexane and dried in vacuo.This gave 3.4 g (83% of theory) of a pale beige powder of the formula(LXIX) with X⁻=BF₄ ⁻.

[0225] In an electrochromic device in accordance with Example 29-30 agreenish blue coloration with λ_(max)=466 and 407 nm was obtained.

Example 3

[0226] a) 45.3 g of 2-metlylthiobenzothiazole were dissolved in 75 ml oftoluene. 151 ml of 1,4-dibromobutane and a spatula tip of potassiumiodide were added. The mixture was boiled for 4 h and then cooled. Itwas filtered, and the solid product was washed with 50 ml of toluene.The filtrate was heated to 50° C., and 35.9 ml of dimethyl sulphate wereadded. This mixture was stirred at 50° C. for 8 h and cooled, and thesolid product was filtered off with suction and washed with 250 ml oftoluene. The product was stirred up in 100 ml of acetone, filtered offwith suction again and washed with 300 ml of acetone. Drying in vacuogave 53.1 g (50% of theory) of the salt of the formula

[0227] b) Under a nitrogen atmosphere, 6.95 g of the benzothiazoliumsalt of the formula (LXX) from a) and 2.9 g of the hydrazone of theformula

[0228] (from Aldrich Chemical Company Ltd., England) were suspended in60 ml of acetonitrile. 2.3 ml of triethylamine were added at roomtemperature. This briefly produced a solution, after which a precipitateformed. After 5 h at room temperature this precipitate was finallyfiltered off with suction, washed with 50 ml of methanol, 100 ml ofwater and a further 50 ml of methanol until the runoff was colourless,and was dried in vacuo. This gave 6.0 g (83% of theory) of the azine ofthe formula

[0229] c) Operating as in Example 1 a) but using 6.8 ml of butyl bromideinstead of benzyl bromide gave 5.2 g (57% of theory) of the pyridiniumsalt of the formula

[0230] d) 2.0 g of the azine of the formula (LXXII) from b) and 1.3 g ofthe pyridinium salt of the formula (LXXIII) from c) were stirred in 20ml of N-methyl-2-pyrrolidone at 80° C. under a nitrogen atmosphere for102 h After the mixture had cooled, a greenish crystalline product wasfiltered off with suction and washed with 50 ml of acetone. Drying gave0.25 g (7.6% of theory) of the dipyridinium salt of the formula

[0231] with X⁻=Br⁻.

[0232] e) 0.25 g of the product from c) was dissolved almost completelyin 5 ml of methanol. 0.45 g of sodium cyanotriphenylborate was added.The mixture was stirred at room temperature for 17 h, during which theproduct gradually became crystalline. This product was filtered off withsuction and washed with 25 ml of methanol, 25 ml of water and again with25 ml of methanol. Drying gave 0.15 g (59% of theory) of a pale greypowder of the formula (LXXIV) with X⁻=NC—B(C₆H₅)₃ ⁻.

[0233] In an electrochromic device in accordance with Example 29-30 agreen coloration with λ_(max)=402; 606; 734 nm was obtained.

Example 4

[0234] a) 4.0 g of the phenothiazine of the formula (LXV) from Example1b) and 0.95 g of 4,4′-bipyridyl were stirred in 10 ml of acetonitrileat 70° C. under a nitrogen atmosphere for 9 h. The suspension was thendiluted with 10 ml of N-methyl-2-pyrrolidone and was stirred at 70° C.for 25 h and at 80° C. for 7 h. After cooling, the mixture was filteredwith suction and the solid product was washed with 50 ml of methanol anddried in vacuo. This gave 1.6 g (32% of theory) of the dipyridinium saltof the formula

[0235] with X⁻=Br⁻.

[0236] b) 1.4 g of the salt of the formula (LXXV) from a) were partlydissolved in 20 ml of methanol under reflux. 2.5 g of sodiumtetraphenylborate were added. The mixture was boiled for 5 minutes moreand then cooled with stirring. The precipitated product was filtered offwith suction, washed with 50 ml of methanol, 50 ml of water and againwith 50 ml of methanol and dried in vacuo. This gave 1.1 g (77% oftheory) of the dipyridinium salt of the formula (LXXV) with X⁻=B(C₆H₅)₄⁻.

[0237] In an electrochromic device in accordance with Example 29-30 ablue-violet coloration with λ_(max)=517 and 606 nm was obtained.

[0238] The examples which follow were prepared in an entirely analogousmanner. MW cagelike Example OX₂-B-RED₁ Colour Anion charge  6

blue-violet 291 −  7

greenish blue 207 −  8

green 133 +  9

green 247 − 10

blue 269 − 11

violet 286 − 12

blue 233 − 13

reddish blue 318.8 − 14

green 147 + 15

violet 302.8 − 16

green 267.8 − 17

green 283 − 18

blue 299 − 19

reddish blue 499 − 20

violet 252 − MW cagelike Example RED₁-B-OX₂-B-RED₁ Colour Anion charge21

greenish blue 319 − 22

blue 133 + 23

green 325 − OX₂-B-RED₁-B-OX₂ 24

greenish blue 312 − MW cagelike Example RED₁-B-OX₂-B-RED₁ Colour Anioncharge 25

violet 382.8 − 26

green 225 − 27

greenish blue 319 − 28

blue- green 225 −

Example 29

[0239] A cell as described in U.S. Pat. No. 4,902,108 was constructedfrom two glass plates, coated with indium tin oxide (ITO), and a sealingring. Under a nitrogen atmosphere, this cell was filled by way of anaperture in the sealing ring with a 0.03 molar solution in anhydrousglutaronitrile of the electrochromic substance of the formula (LXXIV)with X^(θ)=NC—B(C₆H₅)₃ ^(θ) as in Example 3. The cell was sealed so asto be airtight. The solution in the cell was pale yellow. When a voltageof 1.5 V was applied the solution changed colour rapidly to an intensegreen. When the voltage was switched off, the contents of the celldecoloured fully again within 1 minute. Short-circuiting of the cellresulted in more rapid decolouring.

[0240] When the cell was placed upright, the green coloration was stillof uniform intensity over the entire cell area even after operation at1.5 V for 3 h. After being switched off and short-circuited, the celldecoloured rapidly and uniformly over its entire area

Example 30

[0241] A cell was constructed as in Example 29. One of the glass plates,however, was mirrored on the side facing away from the ITO coat.

[0242] This cell was filled under an N₂ atmosphere with a 0.03 molarsolution in anhydrous propylene carbonate of the electrochromicsubstance of the formula (LXIX) with X^(θ)=C₁₂H₂₅—C₆H₄—SO₃ ^(θ) as inExample 2. The colour of the solution in the cell was pale yellow. Whena voltage of 0.9 V was applied the solution changed colour rapidly to adeep greenish blue; after the supply of current had been switched offand the cell short-circuited, the contents of the cell decoloured againwithin about 10 s to give the original pale yellow. More than 100,000such operating cycles were survived without any changes whatsoever.

[0243] When the cell was placed upright, the green coloration was stillof uniform intensity over the entire cell area even after operation at0.9 V for 3 days. After being switched off and short-circuited, the celldecoloured uniformly in the course of 10 s over its entire area.

Example 30a Comparative Example

[0244] The procedure as described in Example 30 was followed but usingthe electrochromic substance of the formula (LXIX) with X⁻=BF₄ ⁻ as inExample 2a. The colour of the solution in the cell was pale yellow. Whena voltage of 0.9 V was applied the solution changed colour rapidly to adeep greenish blue; after the supply of current had been switched offand the cell short-circuited, the contents of the cell decoloured againwithin 10 s to give the original pale yellow. More than 100,000 suchoperating cycles were survived without any changes whatsoever.

[0245] When the cell was placed upright, within just 1 h a blue stripewas formed at the upper edge of the cell and a greenish yellow stripe atthe lower edge of the cell, while the central zone of the cell remainedblue. This state was maintained even throughout the course of prolongedoperation. The two stripes each made up about ¼ of the vertical heightof the cell. After being switched off and short-circuited, the celldecoloured in the course of 10 s in the central zone of the cell. Theblue and greenish yellow stripes at the top and bottom, respectively,however, remained. Only after 2-3 h had these stripes too returnedcompletely to their pale coloration.

Example 31

[0246] An ITO-coated glass plate was sprayed on the coated side with acommercial photoresist, such as Positiv 20 from Kontakt Chemie,Iffezheim and dried in the dark at 50 to 70° C. for 1 h. The resist coatwas then covered with a film containing—as shown in FIG. 1—blacksegments in a transparent surround. This film was printed with a laserprinter to a computer-produced original. The photoresist coat was thenexposed through this film to UV light (from a mercury lamp, e.g. HBO200W/2 from Osram or from a high-pressure xenon lamp XBO 75W/2 fromOsram) for 1 to 5 minutes. The film was removed and the resist coat wastreated in a bath of caustic soda (7 g of sodium hydroxide per litre ofwater) so that the exposed areas were rinsed away. The pretreated glassplate was then placed in a bath of 67 g of FeCl₂×4 H₂O, 6 g of SnCl₂×2H₂O, 104 ml of water and 113 ml of 37 per cent by weight hydrochloricacid, thereby removing the ITO coat at the resist-free, formerly exposedareas. The remaining resist coat was removed with acetone. This gave aglass plate (1) bearing segments (4), conductor connections (3) andcontacts (2).

[0247] A rectangular ring was cut out from a 0.2 mm thick polyethylenefilm. A section about 1-2 cm long was removed (5) from one of its longsides. This film was then placed onto the ITO-coated side of a secondglass plate (7). On the outside of the film—with the exception of theaperture (6)—there was applied a two-component adhesive, for exampleUHU® plus endfest 300 from UHU GmbH, Bühl in Baden. The etched glassplate (1) prepared as described above was then placed onto the film insuch a way that the ITO coat lay on the side of the film (see FIG. 2).The two-component adhesive was then cured, if appropriate by gentleheating to about 40° C.

[0248] The cell was then filled under a nitrogen or argon atmospherewith a solution of 220 mg of the electrochromic compound of the formula

[0249] in 10 ml of anhydrous propylene carbonate, which had beenprepared under a nitrogen or argon atmosphere, by way of the aperture(6), using, for example, a fine pipette or using vacuum to draw in thesolution. The filling aperture (6) was then filled with a matching pieceof polyethylene film and sealed tightly with two-component adhesive.

[0250] Applying a voltage of 0.8 V to the contacts (2) of the segments,as the cathode, and to the nonetched second plate (7), as the anode,resulted in rapid development of a deep greenish blue image of thecontacted segments In this way it was possible to generate all lettersand numerals which can be depicted by means of seven segments, in a deepgreenish blue on a pale yellow background. Switching off the voltage andshort-circuiting the contacts caused the image to disappear againrapidly

[0251] When this cell was placed upright, the connected segmentsremained a single colour, without any different-coloured edge stripeswhatsoever, even after several hours of operation. After switching offthe voltage and short-circuiting the contacts, the segments decolouredrapidly and uniformly.

[0252] In full analogy with Examples 29-31, electrochromic cells wereconstructed using the electrochromic substances set out in Examples1-28, with similarly good results

1. Electrochromic system comprising at least one oxidizable substanceRED₁ which releases electrons at an anode, and at least one reduciblesubstance OX₂ which accepts electrons at a cathode and in so doingundergo transition from a weakly coloured or colourless form into acoloured form OX₁ and RED₂, respectively, accompanied by an increase inthe absorbance in the visible region of the spectrum, the weaklycoloured or colourless form being restored after charge equalization,characterized in that at least one of the substances RED₁ and OX₂ thatare present are linked covalently to one another via a bridge and inthat at least one anion type X is present which a) has a molar mass >200g/mol, preferably >250 g/mol and/or b) has a cagelike structure. 2.Electrochromic system according to claim 1, characterized in that theanion type X) is the counterion of OX₂ and/or is a constituent of aninert conductive salt.
 3. Electrochromic system according to claims 1and 2, characterized in that the anion type X is a constituent of aninert conductive salt when OX₂ has no positive charge.
 4. Electrochromicsystem according to claims 1 to 3, characterized in that the anion typeX present is C₁₀- to C₂₅-alkanesulphonate, preferably C₁₃- toC₂₅-alkanesulphonate, C₅- to C₁₈-perfluoroalkanesulphonate, preferablyC₄- to C₁₈-perfluoroalkanesulphonate, C₁₃- to C₂₅-alkanoate,benzenesulphonate substituted by nitro, C₄- to C₂₅-alkyl, perfluoro-C₁-to C₈-alkyl, C₁- to C₁₂-alkoxycarbonyl or dichloro, naphthalene- orbiphenylsulphonate each of which is unsubstituted or substituted bynitro, cyano, hydroxyl, C₁- to C₂₅-alkyl, C₁- to C₁₂-alkoxy, amino, C₁-to C₁₂-alkoxycarbonyl or chloro, benzene-, naphthalene- orbiphenyldisulphonate each of which is unsubstituted or substituted bynitro, cyano, hydroxyl, C₁- to C₂₅-alkyl, C₁- to C₁₂-alkoxy, C₁- toC₁₂-alkoxycarbonyl or chloro, benzoate substituted by dinitro, C₆- toC₂₅-alkyl, C₄- to C₁₂-alkoxycarbonyl, benzoyl, chlorobenzoyl or toluoyl,or the anion of naphthalenedicarboxylic acid, diphenyl etherdisulphonate, tetraphenylborate, cyanotriphenylborate, tetra-C₃- toC₂₀-alkoxyborate, tetraphenoxyborate, 7,8- or7,9-dicarba-nido-undecaborate(1-) or (2-), each of which isunsubstituted or substituted on the B and/or C atoms by one or two C₁-to C₁₂-alkyl or phenyl groups, dodecahydrodi-carbadodecaborate(2-) orB-C₁- to C₁₂-alkyl-C-phenyl-dodecahydrodicarba-dodecaborate(1-). 5.Electrochromic system according to claims 1 to 4, characterized in thatit comprises at least one electrochromic substance of the formula (I)YB-Z_(a)B-Y_(b)_(c)B-Z   (I), in which Y and Z independently ofone another represent a radical OX₂ or RED₁, subject to the proviso thatat least one Y represents OX₂ and at least one Z represents RED₁, whereOX₂ represents the radical of a reversibly electrochemically reducibleredox system, and RED₁ represents the radical of a reversiblyelectrochemically oxidizable redox system, B represents a bridge memberc represents an integer from 0 to 5, and a and b independently of oneanother represent an integer from 0 to
 5. 6. Electrochromic systemaccording to claims 1 to 5, characterized in that it comprises at leastone electrochromic substance of the formula (I) in which Y representsOX₂ and Z represents RED₁ and Y and Z alternate in their sequence. 7.Electrochromic system according to claims 1 to 6, characterized in thatit comprises at least one electrochromic substance of the formulaOX₂-B-RED₁   (Ia), OX₂-B-RED₁-B-OX₂   (Ib), RED₁-B-OX₂-B-RED₁   (Ic), orOX₂-(B-RED₁-B-OX₂)_(d)-B-RED₁   (Id), in which OX₂, RED₁ and B have themeaning indicated above and d represents an integer from 1 to
 5. 8.Electrochromic system according to claims 1 to 7, characterized in thatit comprises at least one electrochromic substance of the formulae(Ia)-(Id) in which OX₂ represents the radical of a cathodicallyreducible substance which in its cyclic voltammogram, recorded in aninert solvent at room temperature, exhibits at least two chemicallyreversible reduction waves, the first of these reduction waves leadingto an increase in the absorbance at least one wavelength in the visibleregion of the electromagnetic spectrum, RED₁ represents the radical ofan anodically reversibly oxidizable substance which in its cyclicvoltammogram, recorded in an inert solvent at room temperature, exhibitsat least two chemically reversible oxidation waves, the first of theseoxidation waves leading to an increase in the absorbance at least onewavelength in the visible region of the electromagnetic spectrum, and Brepresents a bridge.
 9. Electrochromic system according to claims 1 to8, characterized in that it comprises at least one substance of theformula (Ia)-(Id) in which OX₂ represents a radical of the formula

where R² to R⁵, R⁸, R⁹, R¹⁶ to R¹⁹ independently of one another denoteC₁- to C₁₈-alkyl, C₂- to C₁₂-alkenyl, C₃- to C₇-cycloalkyl, C₇- toC₁₅-aralkyl or C₆- to C₁₀-aryl, or R⁴ and R⁵ or R⁸ and R⁹ together forma —(CH₂)₂— or —(CH₂)₃— bridge, R⁶, R⁷ and R²² to R²⁵ independently ofone another denote hydrogen, C₁- to C₄-alkyl, C₁- to C₄-alkoxy, halogen,cyano, nitro or C₁- to C₄-alkoxycarbonyl, or R²² and R²³ and/or R²⁴ andR²⁵ form a —CH═CH—CH═CH— bridge, R¹⁰ and R¹¹; R¹² and R¹³; R¹⁴ and R¹⁵independently of one another denote hydrogen or in pairs denote a—(CH₂)₂—, —(CH₂)₃— or —CH═CH—bridge, R⁶⁹ to R⁷⁴ independently of oneanother denote hydrogen or C₁-C₆-alkyl, or R⁶⁹; R¹² and/or R⁷⁰; R¹³ forma —CH═CH—CH═CH— bridge, R²⁰ and R²¹ independently of one another denoteO, N—CN, C(CN)₂ or N—C₆- to C₁₀-aryl, R²⁶ denotes hydrogen, C₁- toC₄-alkyl, C₁- to C₄-alkoxy, halogen, cyano, nitro, C₁- toC₄-alkoxycarbonyl or C₆- to C₁₀-aryl, E¹ and E² independently of oneanother denote O, S, NR¹ or C(CH₃)₂, or E¹ and E² together form an—N—(CH₂)₂—N— bridge, R¹ denotes C₁- to C₁₈-alkyl, C₂- to C₁₂-alkenyl,C₄- to C₇-cycloalkyl, C₇- to C₁₅-aralkyl, C₆- to C₁₀-aryl, Z¹ denotes adirect bond, —CH═CH—, —C(CH₃)═CH—, —C(CN)═CH—, —CCl═CCl—, —C(OH)═CH—,—CCl═CH—, —C═C—, —CH═N—N═CH—, —C(CH₃)═N—N═C(CH₃)— or —CCl═N—N═CCl—, Z²denotes —(CH₂)_(r)— or —CH₂—C₆H₄—CH₂—, r denotes an integer from 1 to 10and X represents an anion which is redox-inert under the conditions andwhich a) has a molar mass >200 g/mol, preferably >250 g/mol and/or b)has a cagelike structure, where the bond to the bridge B is via one ofthe radicals R²-R¹⁹, R²²-R²⁷ or, if E¹ or E² represents NR¹, is via R¹,and the radicals mentioned in that case represent a direct bond, RED₁represents one of the following radicals

in which R²⁸ to R³¹, R³⁴, R³⁵, R³⁸, R³⁹, R⁴⁶, R⁵³ and R⁵⁴ independentlyof one another denote C₁- to C₁₈-alkyl, C₂- to C₁₂-alkenyl, C₃- toC₇-cycloalkyl, C₇- to C₁₅-aralkyl or C₆- to C₁₀-aryl, and R⁴⁶, R⁵³ andR⁵⁴ additionally denote hydrogen, R³², R³³, R³⁶, R³⁷, R⁴⁰, R⁴¹, R⁴² toR⁴⁵, R⁴⁷, R⁴⁸, R⁴⁹ to R⁵² and R⁵⁵ to R⁵⁷ independently of one anotherdenote hydrogen, C₁- to C₄-alkyl, C₁- to C₄-alkoxy, halogen, cyano,nitro, C₁- to C₄-alkoxycarbonyl or C₆- to C₁₀-aryl and R⁵⁷ and R⁵⁸additionally denote an optionally benzo-fused aromatic or quasi-aromaticfive- or six-membered heterocyclic ring and R⁴⁸ additionally denotesNR⁷⁵R⁷⁶, R⁴⁹ and R⁵⁰ and/or R⁵¹ and R⁵² form a —(CH₂)₃—, —(CH₂)₄—,—(CH₂)₅— or —CH═CH—CH═CH— bridge, Z³ denotes a direct bond, a —CH═CH— or—N═N— bridge, ═Z⁴═ denotes a direct double bond, a ═CH—CH═ or ═N—N═bridge, E³ to E⁵, E¹⁰ and E¹¹ independently of one another denote O, S,NR⁵⁹ or C(CH₃)₂, and E⁵ additionally denotes C═O or SO₂, or E³ and E⁴independently of one another denote —CH═CH—, E⁶ to E⁹ independently ofone another denote S, Se or NR⁵⁹, R⁵⁹, R⁷⁵ and R⁷⁶ independently of oneanother denote C₁- to C₁₂-alkyl, C₂- to C₈-alkenyl, C₃- toC₇-cycloalkyl, C₇- to C₁₅-aralkyl or C₆- to C₁₀-aryl, and R⁷⁵additionally denotes hydrogen, or R⁷⁵ and R⁷⁶ in the definition ofNR⁷⁵R⁷⁶ form, together with the N atom to which they are attached, afive- or six-membered, saturated ring which can contain furtherheteroatoms, R⁶¹ to R⁶⁸ independently of one another denote hydrogen,C₁- to C₆-alkyl, C₁- to C₄-alkoxy, cyano, C₁- to C₄-alkoxycarbonyl orC₆- to C₁₀-aryl, or R⁶¹; R⁶² and R⁶⁷, R⁶⁸ independently of one another,together form a —(CH₂)₃—, —(CH₂)₄— or —CH═CH—CH═CH— bridge, v denotes aninteger between 0 and 10, the bond to the bridge B being via one of theradicals R²⁸-R⁵⁸, R⁶¹, R⁶², R⁶⁷, R⁶⁸ or, if one of the radicals E³-E¹¹represents NR⁵⁹, is via R⁵⁹ and the abovementioned radicals in that caserepresent a direct bond, and B represents a bridge of the formula—(CH₂)_(n)— or —[Y¹ _(s)(CH₂)_(m)—Y²]_(o)—(CH₂)_(p)—Y³ _(q)—, each ofwhich is unsubstituted or substituted by C₁- to C₄-alkoxy, halogen orphenyl, Y¹ to Y³ independently of one another represent O, S, NR⁶⁰, COO,CONH, NHCONH, cyclopentadienyl, cyclohexanediol, phenylene ornaphthylene, R⁶⁰ denotes C₁- to C₆-alkyl, C₂- to C₆-alkenyl, C₄- toC₇-cycloalkyl, C₇- to C₁₅-aralkyl or C₆- to C₁₀-aryl, n denotes aninteger from 1 to 12, m and p independently of one another denote aninteger from 0 to 8, o denotes an integer from 0 to 6, and q and sindependently of one another denote 0 or 1, and, if OX₂ has no positivecharge, there is at least one conductive salt present which comprisesthe abovementioned anion X⁻.
 10. Electrochromic system according toclaims 1 to 9, characterized in that it comprises at least one substanceof the formula (Ia)-(Id) in which OX₂ represents a radical of theformula (N), (III), (IV) or (V) where R², R³, R⁴, R⁵, R⁸ and R⁹independently of one another represent C₁- to C₁₂- alkyl, C₂- toC₈-alkenyl, C₅- to C₇-cycloalkyl, C₇- to C₁₅-aralkyl or C₆- to C₁₀-aryl,R⁶ and R⁷ independently of one another represent hydrogen, methyl,ethyl, methoxy, ethoxy, fluoro, chloro, bromo, cyano, nitro,methoxy-carbonyl or ethoxycarbonyl, R¹⁰, R¹¹; R¹², R¹³ and R¹⁴, R¹⁵independently of one another represent hydrogen or, if Z¹ denotes adirect bond, in each case in pairs together represent a —(CH₂)₂—,—(CH₂)₃— or —CH═CH— bridge, or R⁴, R⁵ and R⁸, R⁹ independently of oneanother in each case in pairs together represent a —(CH₂)₂— or —(CH₂)₃—bridge if Z¹ denotes a direct bond, R⁶⁹ to R⁷⁴ independently of theanother denote hydrogen or C₁-C₄-alkyl, E¹ and E² are identical andrepresent O, S, NR¹ or C(CH₃)₂ or together form an —N—(CH₂)₂—N— bridge,R¹ represents C₁- to C₁₂-alkyl, C₂- to C₄-alkenyl, C₅- to C₇-cycloalkyl,C₇- to C₁₅-aralkyl or C₆- to C₁₀-aryl, Z¹ represents a direct bond,—CH═CH—, —C(CH₃)═CH—, —C(CN)═CH—, —C═C— or —CH═N—N═CH—, Z² represents—(CH)_(r)— or —CH₂—C₆H₄—CH₂—, r represents an integer between 1 and 6, Xrepresents C₁₀- to C₂₅-alkanesulphonate, preferably C₁₃- toC₂₅-alkanesulphonate, C₅- to C₁₈-perfluoroalkanesulphonate, preferablyC₄- to C₁₈-perfluoroalkanesulphonate, C₁₃- to C₂₅-alkanoate,benzenesulphonate substituted by nitro, C₄- to C₂₅-alkyl, perfluoro-C₁-to C₈-alkyl, C₁- to C₁₂-alkoxycarbonyl or dichloro, naphthalene- orbiphenylsulphonate each of which is unsubstituted or substituted bynitro, ayano, hydroxyl, C₁- to C₂₅-alkyl, C₁- to C₁₂-alkoxy, amino, C₁-to C₁₂-alkoxycarbonyl or chloro, benzene-, naphthalene- orbi-phenyldisulphonate each of which is unsubstituted or substituted bynitro, cyano, hydroxyl, C₁- to C₂₅-alkyl, C₁- to C₁₂-alkoxy, C₁- toC₁₂-alkoxycarbonyl or chloro, benzoate substituted by dinitro, C₆- toC₂₅-alkyl, C₄- to C₁₂-alkoxycarbonyl, benzoyl, chlorobenzoyl or toluoyl,or the anion of naphthalenedicarboxylic acid, diphenyl etherdisulphonate, tetraphenylborate, cyanotriphenylborate, tetra-C₃- toC₂₀-alkoxyborate, tetraphenoxyborate, 7,8- or7,9-dicarba-nido-undecaborate(1-) or (2-), each of which isunsubstituted or substituted on the B and/or C atoms by one or two C₁-to C₁₂-alkyl or phenyl groups, dodecahydrodicarbadodecaborate(2-) orB-C₁- to C₁₂-alkyl-C-phenyl-dodecahydrodicarbadodecaborate(1-), where inthe case of polyvalent anions such as naphthalenedisulphonate X⁻represents one equivalent of this anion, where the bond to the bridge Bis via one of the radicals R²-R¹¹ or, if E¹ or E² represents NR¹, is viaR¹, and the abovementioned radicals in that case represent a directbond, RED₁ represents a radical of the formula (X), (XI), (XII), (XIII),(XVI), (XVII), (XVIII) or (XX), where R²⁸ to R³¹, R³⁴, R³⁵, R³⁸, R³⁹,R⁴⁶, R⁵³ and R⁵⁴ independently of one another denote C₁- to C₁₂-alkyl,C₂- to C₈-alkenyl, C₅- to C₇-cycloalkyl, C₇- to C₁₅-aralkyl or C₆- toC₁₀-aryl and R⁴⁶, R⁵³ and R⁵⁴ additionally denote hydrogen, R³², R³³,R³⁶, R³⁷, R⁴⁰, R⁴¹, R⁴⁷ to R⁵², R⁵⁵ and R⁵⁶ independently of one anotherdenote hydrogen, methyl, ethyl, methoxy, ethoxy, fluoro, chloro, bromo,cyano, nitro, methoxycarbonyl, ethoxycarbonyl or phenyl, and R⁵⁷ and R⁵⁸additionally denote 2- or 4-pyridyl, and R⁴⁸ additionally denotesNR⁷⁵R⁷⁶, Z³ denotes a direct bond, a —CH═CH— or —N═N— bridge, ═Z⁴═denotes a direct double bond, a ═CH—CH═ or ═N—N═ bridge, E³ to E⁵, E¹⁰and E¹¹, independently of one another denote O, S, NR⁵⁹ or C(CH₃)₂, butE³ and E⁴ have the same meaning, E⁶ to E⁹ are identical to one anotherand denote S, Se or NR⁵⁹, and E⁵ additionally denotes C═O, E⁶ representsNR⁵⁹, where R⁵⁹ denotes a direct bond to the bridge B, and E⁷ to E⁹possess the meaning indicated above, but need not be identical to oneanother, R⁵⁹, R⁷⁵ and R⁷⁶ independently of one another denote C₁- toC₁₂-alkyl, C₂- to C₈-alkenyl, C₅- to C₇-cycloalkyl, C₇- to C₁₅-aralkylor C₆- to C₁₀-aryl, and R⁷⁵ additionally denotes hydrogen, or R⁷⁵ andR⁷⁶ in the definition of NR⁷⁵R⁷⁶ denote, together with the N atom towhich they are attached, pyrrolidino, piperidino or morpholino, R⁶¹, R⁶²and R⁶⁷, R⁶⁸ independently of one another represent hydrogen, C₁- toC₄-alkyl, methoxycarbonyl, ethoxycarbonyl or phenyl, or in pairstogether represent a —(CH₂)₃— or —(CH₂)₄— bridge, R⁶³ to R⁶⁶ representhydrogen, and v represents an integer from 1 to 6, where the bond to thebridge B is via one of the radicals R²⁸—R⁴¹, R⁴⁶—R⁵⁶, R⁶¹, R⁶², R⁶⁷, R⁶⁸or, if one of the radicals E³-E¹¹ represents NR⁵⁹, is via R⁵⁹, and theabovementioned radicals in that case represent a direct bond, Brepresents a bridge of the formulae —(CH₂)_(n)—,—(CH₂)_(m)—O—(CH₂)_(p)—, —(CH)_(m)—NR⁶⁰—(CH₂)_(p)—,—(CH₂)_(m)—C₆H₄—(CH₂)_(p)—, —[O—(CH₂)_(p)]_(o)—O—,—[NR⁶⁰—(CH₂)_(p)]_(o)—NR⁶⁰—, —[C₆H₄—(CH₂)_(p)]_(o)—C₆H₄—,—(CH₂)_(m)—OCO—C₆H₄—COO—(CH₂)_(p)—,—(CH₂)_(m)—NHCO—C₆H₄—CONH—(CH₂)_(p)—,—(CH₂)_(m)—NHCONH—C₆H₄NHCONH—(CH₂)_(p)—,—(CH₂)_(m)—OCO—(CH₂)_(t)—COO—(CH₂)—,—(CH₂)_(m)—NHOO—(CH₂)_(t)—CONH—(CH)_(p)—,—(CH₂)_(m)—NHCONH—(CH₂)_(t)—NHCONH—(CH₂)_(p)—, R⁶⁰ represents methyl,ethyl, benzyl or phenyl, n represents an integer from 1 to 10, m and pindependently of one another represent an integer from 0 to 4, orepresents an integer from 0 to 2, and t represents an integer from 1 to6.
 11. Electrochromic system according to claims 1 to 10, characterizedin that it comprises at least one substance of the formula (Ia)-(Id) inwhich OX₂ represents a radical of the formula (II), (IV) or (V) in whichR², R⁴ and R⁸ represent a direct bond to the bridge B, R³, R⁵ and R⁹independently of one another represent methyl, ethyl, propyl, butyl,pentyl, hexyl, heptyl, octyl, benzyl or phenyl, or R³, R⁵ and R⁹ in thecase of the formulae Ic and Id also represent a direct bond to thebridge B, R⁶ and R⁷ are identical and represent hydrogen, methyl,methoxy, chloro, cyano or methoxycarbonyl, R¹⁰, R¹¹; R¹², R¹³ and R¹⁴,R¹⁵ independently of one another represent hydrogen or, if Z¹ denotes adirect bond, represent, in each case in pairs together, a —CH═CH—bridge, R⁶⁹ to R⁷² are identical and denote hydrogen, methyl or ethyl,R⁷³ and R⁷⁴ denote hydrogen, E¹ and E² are identical and represent O orS, Z¹ represents a direct bond or —CH═CH—, X³¹ represents C₁₅- toC₂₂-alkanesulphonate, C₈- to C₁₂-perfluoroalkane-sulphonate,nitrobenzenesulphonate, dinitrobenzenesulphonate, mono- or bis-C₄- toC₁₂-alkylbenzenesulphonate, dichlorobenzene-sulphonate,naphthalenesulphonate, nitronaphthalenesulphonate,di-nitronaphthalenesulphonate, mono- or bis-C₃- toC₁₂-alkyl-naphthalenesulphonate, hydroxynaphthalenesulphonate,amino-naphthalenesulphonate, biphenylsulphonate, benzenedisulphonate,nitrobenzenedisulphonate, C₄- to C₁₂-alkylbenzenedisulphonate,naphthalenedisulphonate, nitronaphthalenedisulphonate, C₄- toC₁₂-alkylnaphthalenedisulphonate, biphenyldisulphonate, dinitrobenzoate,mono- or bis-C₈- to C₁₂-alkylbenzoate, C₆- toC₁₂-alkoxycarbonyl-benzoate, benzylbenzoate, toluoylbenzoate, the anionof naphthalenedicarboxylic acid, cyanotriphenylborate, tetra-C₄- toC₁₂-alkoxyborate, tetraphenoxyborate, 7,8- or7,9-dicarba-nido-unde-caborate(1-) or (2-) each of which isunsubstituted or substituted on the B and/or C atoms by one or twomethyl, ethyl, butyl or phenyl groups,dodecahydrodicarbado-dodecaborate(2-) orB-methyl-C-phenyl-dodecahydrodi-dicarbadodecaborate(1-), where in thecase of polyvalent anions such as naphthalenedisulphonate X representsone equivalent of this anion, RED₁ represents a radical of the formula(X), (XII), (XIII), (XVI) or (XVII), R²⁸, R³⁴, R³⁸, R⁴⁶ and R⁴⁹represent a direct bond to the bridge B, R²⁹ to R³¹, R³⁵ and R³⁹independently of one another represent methyl, ethyl, propyl, butyl,pentyl, hexyl, heptyl, octyl, benzyl or phenyl, or R³⁰, R³⁵ and R³⁹ inthe case of the formulae Ib and Ic, also represent a direct bond to thebridge B, R³², R⁴⁷ and R⁴⁸ represent hydrogen, R³⁶, R³⁷, R⁴⁰, R⁴¹ andR⁵⁰ to R⁵² independently of one another represent hydrogen, methyl,methoxy, chloro, cyano, methoxycarbonyl or phenyl, or R⁵¹ in the case ofthe formulae Ib and Id, also represents a direct bond to the bridge B,Z³ represents a direct bond, a —CH═CH— or —N═N— bridge, ═Z⁴═ representsa direct double bond, a ═CH—CH═ or ═N—N═ bridge, E³ to E⁵ independentlyof one another represent O, S or NR⁵⁹, but E³ and E⁴ have the samemeaning, E⁶ to E⁹ are identical to one another and represent S, Se orN⁵⁹, R⁵⁹ represents methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl,octyl, benzyl or phenyl, or R⁵⁹ in the case of the formula XVI informula Ib and Id, also represents a direct bond to the bridge B, Brepresents a bridge of the formulae —(CH₂)_(n)—, —(CH₂)_(m)—O(CH₂)_(p)—,—(CH₂)_(m)—NR⁶⁰—(CH₂)_(p)—, —(CH₂)_(m)—C₆H₄—(CH₂)_(p)—, —O—(CH₂)_(p)—O—,—NR⁶⁰—(CH₂)_(p)—NR⁶⁰—, —(CH₂)_(m)—OCO—C₆H₄—COO—(CH₂)_(p)—,—(CH₂)_(m)—NHCO—C₆H₄—CONH—(CH₂)_(p)—,—(CH₂)_(m)—NHCONH—C₆H₄—NHCONH—(CH₂)_(p)—,—(CH₂)_(m)—OCO—(CH₂)_(t)—COO—(CH₂)_(p)—,—(CH₂)_(m)—NHCO—(C₂)_(t)—CONH—(CH₂)_(p)—,—(CH₂)_(m)—NHCONH—(CH₂)_(t)—NHCONH—(CH₂)_(p)—, R⁶⁰ represents methyl, nrepresents an integer from 1 to 10, m and p are identical and representan integer from 0 to 2, and t represents an integer from 1 to
 6. 12.Electrochromic system according to claims 1 to 11, characterized in thatit comprises at least one electrochromic substance of the formula (Ia)OX₂—B—RED₁   (Ia) corresponding to one of the formulae

or at least one substance of the formula (Ic) corresponding to one ofthe formulae

in which R³, R⁵, R³⁵ and R³⁹ independently of one another representmethyl, ethyl, propyl, butyl, pentyl, hexyl or benzyl, R⁶, R⁷ and R³⁶,R³⁷ in pairs are identical and represent hydrogen, methyl, methoxy,chloro, cyano or methoxycarbonyl, R¹² and R¹³ represent hydrogen or, ifZ¹ denotes a direct bond, together represent a —CH═CH— bridge, R⁶⁹ toR⁷² are identical and represent hydrogen or methyl, E¹ and E² areidentical and represent O or S, Z¹ represents a direct bond or —CH═CH—,R³², R⁴⁷ and R⁴⁸ represent hydrogen, E³ to E⁵ independently of oneanother represent O, S or NR⁵⁹, but E³ and E⁴ are identical, R²⁹ to R³¹and R⁵⁹ independently of one another represent methyl, ethyl, propyl,butyl, pentyl, hexyl or benzyl, where R²⁹ to R³¹ are preferablyidentical, R⁴⁰ and R⁴¹ are identical and represent hydrogen, methyl,ethyl, propyl, butyl or phenyl, Z³ represents a direct bond, —CH═CH— or—N═N—, R⁵⁰ to R⁵² independently of one another represent hydrogen,methyl, methoxy, chloro, cyano, methoxycarbonyl, ethoxycarbonyl orphenyl, but are preferably identical, E⁶ to E⁹ are identical to oneanother and represent S, Se or NR⁵⁹, Z⁴ represents a direct double bond,a ═CH—CH═ or ═N—N═ bridge, m represents an integer from 1 to 5, urepresents 0 or 1 and X⁻ represents C₁₅- to C₂₀-alkanesulphonate, C₅- toC₈-perfluoroalkane-sulphonate, mono- or dibutylbenzenesulphonate, mono-or di-tert-butylbenzenesulphonate, octylbenzenesulphonate,dodecylbenzene-sulphonate, naphthalenesulphonate, biphenylsulphonate,nitro-benzenedisulphonate, naphthalenedisulphonate,dibutylnaphthalene-sulphonate, biphenyldisulphonate, benzoylbenzoate,cyanotri-phenylborate, tetra-C₃- to C₈-alkoxyborate, tetraphenoxyborate,7,8-or 7,9-dicarba-nido-undecaborate(1-) or (2-) ordodecahydrodi-di-carbadodecaborate(2-), where in the case of polyvalentanions such as naphthalenedisulphonate X⁻ represents one equivalent ofthis anion.
 13. Electrochromic substance corresponding to the formulaYB-Z_(a)B-Y_(b)_(c)B-Z   (I) in which Y and Z independently of oneanother represent a radical OX₂ or RED₁, subject to the proviso that atleast one Y represents OX₂ and at least one Z represents RED₁, where OX₂represents the radical of a reversibly electrochemically reduciblecationic redox system which comprises as its counterion an anion X⁻according to claim 1, and RED₁ represents the radical of a reversiblyelectrochemically oxidizable redox system.
 14. Electrochromic fluidcomprising an electrochromic system according to at least one of claims1 to 12 and at least one inert solvent.
 15. Electrochromic devicecomprising an electrochromic fluid according to claim
 14. 16.Electrochromic device according to claim 15, characterized in that it isconfigured as a cell, such as a solar cell, for example, or as a windowpane, mirror, sunroof or display.
 17. Electrochromic device according toclaims 15 and 16, characterized in that it consists of two facing,transparent glass or plastic plates of which one may be mirrored andwhose facing sides carry an electroconductive coating, between whichplates the electrochromic fluid is contained.